This invention relates to a machine for preparing "espresso" coffee, particularly for use as a home appliance, of the type having a container for the water to be heated in order to form the beverage upon percolation under pressure through a layer of powdered coffee, and a percolation chamber connected to the water container through an interconnecting pipe, the pipe having one end submerged in the water container and another end opening into the percolation chamber through a valve, and being arranged with a portion thereof within a cooling space or receptacle.
The prior art coffee preparing machines of this design suffer from the drawback of operating at pressure levels only slightly above the normal pressure level and of cooling the hot water for the beverage by the introduction of part of said hot water into the cooling space, thereby the cooling step is effected at 100.degree. C. by evaporation, i.e. in a condition where the produced coffee beverage develops a "burned" taste which is quite unpleasant. However, it is generally agreed that the best coffee is prepared with the "espresso" high pressure machines operated by coffee-bars and the like, whereby optimum temperature and pressure conditions are reached and maintained which amount, according to tests purposely carried out, to 89.degree.-92.degree. C. and about 7 to 9 kg/cm.sup.2 gauge pressure, respectively. Such coffee preparing machines, sometimes of reduced overall size for household use, are, however, rather complex since they include mechanical systems, such as pumps, etc. effective to increase the pressure level.
It is a primary object of this invention to obviate the difficulties mentioned above and to provide a coffee preparing machine particularly suited to household use, wherein the hot water for percolation may be obtained at temperature levels approaching the water boiling point (100.degree. C.) and at high pressure.